Often it is desirable to protect documents, especially paper documents, either for placing them under a protective cover from external harmful factors such as humidity (maps, exterior use plans, etc.), or for avoiding the possibility that they could be falsified and making them void (identification papers, administration documents etc.).
At the present time, such protection may be obtained through plastification by heating (such as for example is described in French patent 1,549,724); but, such a process requires professional equipment and is carried out by specialists. These conditions for carrying out the protection process and the cost of the process limit the process to its application to specific, narrow fields (important or valuable documents, small surfaces to be covered, etc.) and exclude the general use for every day documents. Moreover, the plastification produces a covering of the document with a relatively thick layer (based on polyvinyl) and modifies the characteristics of the document which lose a significant part of its flexibility and is no longer pliable or capable of being manipulated as before the covering.
Additionally, it is known in the field of decals to use cellulosic or nitro-cellulosic transfer films (see for example French patent 2,427,208) or films obtained by the deposition of an alkyd-urethane (see for example U.S. Pat. No. 4,308,310), which are used for covering a surface of a design. But these marking films are not useful for meeting the objectives of protection intended by the present invention, as they are very fragile and not resistant to even weak solvents and, certainly, not to stronger solvents such as the cellulosic diluents. A particular problem is that these films may be easily removed without altering the support, and therefore do not create a protection against falsification.
The present invention provides a new protective product useful "cold" or at ambient temperature with simple pressure, in the manner of a transfer film, by anyone without any particular equipment. By "cold" is meant that heating is not required to carry out the process.
The primary object of the invention is to provide a product which gives a very secure protection as much with regard to external damaging factors as with regard to falsifications. In particular, the invention provides a product having a transferrable protective film which is resistant to weak solvents as well as to cellulosic solvents, and the removal or attempted removal of which is necessarily accompanied by either a destruction or a very apparent alteration of the document, for most of the materials used, and especially for paper documents.
Another object of the invention is to permit personalizing the document, by adding to it designs or a weave either directly visible or invisible with ordinary light but detectable under ultraviolet radiation.
Another object is to avoid modifying, significantly, the physical characteristics of the protected document, while retaining in the document a flexibility and the possibility of folding, analogous to such properties as are initially possessed by the document.
Still another object of the invention is to provide a process for producing a protective product which benefits from relatively low cost, this cost, combined with the ease of using the product permitting the general utilization of the product with most common documents.
Still a further object of the invention is to provide a process which lends itself to obtaining transferrable protective films intended for diverse functions in accordance with the final use of the product intended.